Aśauca-vidhi (Rules of Impurity) within Śrāddha-kalpa — Chapter on Testing/Selecting Brahmanas and Honoring the Atithi
त्रिवेदो ऽनन्तरं तस्य द्विवेदस्तदनन्तरम् / एकवेदस्ततः पश्चादुपाध्यायस्ततः परम्
trivedo 'nantaraṃ tasya dvivedastadanantaram / ekavedastataḥ paścādupādhyāyastataḥ param
After him comes the knower of three Vedas, then the knower of two Vedas; then the knower of one Veda; and beyond them, the upādhyāya (teaching preceptor)—in due order.